Currently, portable electronics and other devices are provided electric energy via a plug provided with prongs or blades that are inserted into a power outlet. Often, the plug provides some type of power conversion or conditioning, etc., so that the power delivered to the electronic device is in a state that is usable by the electronic device. Most particularly, the plug acts as a converter so that power received from the plug of a certain voltage, as well as preferably a certain current type (i.e., alternating current or direct current) is transmitted to the electronic device with a pre-determined voltage and current type. Towards this end, the plug may receive, e.g., 120 VAC and supply a stepped-down voltage as a direct current, such as 5-20 VDC. The plug, as described, is thus a converter plug and, for electronic devices that are portable and chargeable, the plug is commonly referred to as an ac adapter or charger plug. In order to effect such power conversion, the plug includes internal circuit components, the components then being electrically connected to a power coupling such as a cord that extends from the plug.
There are significant issues with such plugs, such as the size of the plug. Efforts to reduce the plug vertical and lateral dimensions are well-known so that, when the plug prongs are inserted into a power receptacle or outlet or power strip (a power source), the plug itself provides little or no interference with use of an adjacent receptacle. Often times, however, plug designs having reduced vertical and lateral dimensions require an increased plug length (i.e., the dimension of the plug aligned with the direction of the plug prongs). This increased length may hinder the ability of a user to locate the plug in an outlet that is behind, for instance, a furniture item, and may require the plug to protrude in a manner that makes the plug susceptible to being struck, that makes the plug susceptible to backing out of the receptacle due to the torque provided by its own weight, or that makes the plug simply unsightly.
Another issue with such plugs is cost, which is typically a two-fold problem. One aspect of the problem is that packaging material costs for a larger plug are simply greater than for a smaller plug.
The other aspect of the problem is the cost of manufacturing and assembling the plug. In many prior art plugs, the blades (including the prongs receivable in the outlet) are insert molded, which is a relatively expensive process and requires approximately 20 seconds of mold time. To be more specific, the process requires the blades to be positioned in proper registry within a mold cavity. The mold then receives the material for a plug housing in a flowable state (such as by transfer or injection molding, as examples). The material then cools and hardens so that the blades and housing portions can be removed. Because the temperature of the metal blades is elevated, the molding must be cooled sufficiently that the blades do not cause creep in the thermoplastic creep material, which requires time. Nonetheless, errors do result from improper positioning or inadvertent movement of the blades during the molding process, which results in production waste, at least in terms of time and effort.
After the blades are insert molded, they must be joined with the internal circuitry of the plug, that is, the circuitry that provides the power conversion. In most prior art plugs, this requires hand soldering within the plug housing to join connections on the blades with either wires leading to the circuitry or with contacts directly located on the circuitry, such as a printed circuit board (PCB). This process is manually performed and requires patience and care, which translates to labor and time. This process can also result in errors as it is difficult to avoid contact of a solder iron or other implement from contacting the plastic housing (resulting in damage thereto), and as it is difficult to immediately recognize improper solder joints. Additionally, it is difficult to test the plug device for proper operation until after the blades are soldered/secured with the circuitry, at which point removal of defective components is labor intensive.
It should also be noted that use of solder and hookup wire requires packaging space. That is, utilizing solder and hookup wire for electrically connecting the blades to the circuitry requires a minimum solder joint, at least for reliability purposes as well as typically for practical purposes as it is difficult to utilize a small amount of solder. The wire length needs to be long enough to allow soldering while the components are separated. This length of wire takes up space inside the package and can get in the way when closing the package. Accordingly, the packaging and, more precisely, the housing or body of the plug must accommodate such solder joints and hookup wire, resulting in a larger plug package size or dimension directly attributable to the solder joints and hookup wire.
One example of a plug having internal circuitry for AC conversion to DC is described in U.S. Pat. No. 6,644,984, to Vista, Jr., et al. Notably, the '984 patent is directed towards reducing the package size and the profile of the plug, as well as eliminating the need for flexible wires or direct soldering between the blades and the circuitry, which purported results in quicker assembly.
Nonetheless, the various forms of the '984 patent have an elongated plug length due to the manner of connecting the blades with the circuitry. Each of the forms described has a forward body portion in which the blades are mounted, the blades having a rearward extension that is connected, without solder, with contact terminals on a PCB. Each of the contact terminals requires an fore-to-aft extended structure for either forming a leaf spring biased against the blade or supporting a receptacle for receiving a portion of the blade therethrough. In each form, then, the configuration and construction of the blades and the contact terminals require additional length for the plug size and package. Furthermore, the structures for the contact terminals require a certain amount of material and are stamped into form.
The '984 patent also requires additional components and manufacturing steps. While the forms illustrate a manner of connecting the blades without the use of solder, the designs still require blades that are insert molded into the forward body portion. In the simplest form, the manufacturing steps include first securing the PCB in a rear housing/body portion in proper alignment, then advancing the rear body portion and PCB toward and into engagement with the forward body portion and blades molded therein, whereupon the body portions are secured. In more complicated designs, the forward body portion first receives the PCB, and the sub-assembly is then mounted into a clamshell-type rear body portion having top and bottom halves.
Accordingly, there has been a need for an improved plug package design with a reduced size and improved manufacturability.